OBJECTIVES: Our ultimate goal is to apply autologous human mesenchymal stromal stem cells (hMSCs) to repair the injured spinal cord, enabling enhanced functional rehabilitation for America's veterans after spinal cord injury (SCI). Histological and molecular improvements were previously reported in lab SCI models after MSC transplantation; however, to date, few studies showed substantial functional recovery. This attributes largely to the observed low viability and poor localization of implanted cells. We have uncovered that incorporation of neural stem cells into biodegradable polymer scaffolds boosted their survival and neurotrophic impacts in rat SCI, thereby permitting marked functional improvement. Thus, we propose to stabilize hMSCs in poly(lactic-co-glycolic acid) (PLGA) scaffolds in order to test our central hypothesis that hMSC-derived immunomodulatory and neuroplastic effects could be used to impede degeneration and promote repair and neuroplasticity, a bionecessity for SCI rehabilitation. RESEARCH DESIGN: Aim 1 is designed for determining the neurotrophic and immunomodulatory effects of hMSCs seeded in PLGA (1 Year). In Aim 2, we will assess the therapeutic potential of implanting scaffolded hMSCs in acute SCI (1.5 Years). Lastly, Aim 3 studies will determine the therapeutic efficacy of treating chronic SCI with scaffolded hMSCs implanted 70 d post SCI; (1.5 Years). We will first use our in vitro systems to evaluate the biology of hMSCs seeded in PLGA. Systematical characterization will then be done on the impact of providing PLGA support to augment viability of hMSCs at the injury site of a rat model of segmental hemisection SCI. Histological, immunocytochemical and molecular outcomes will be analyzed at 2 or 4 weeks post injury, which will be correlated with functional impairment after subacute and chronic SCI. The studies will be conducted according to a randomized block design. The size of the experimental groups is determined by power analyses previously reported. All outcome values are presented as mean 1 SEM. Application of the term significant in the tests implies p < 0.05. All experimental procedures will be reviewed and approved by the Animal Care and Use Committee of the VA Boston Healthcare System. Behavioral scores, cell survival and immunohistochemical results are analyzed using repeated measures ANOVA, followed by unpaired Student's t tests. Fisher's exact test and paired Student's t test are used for the statistical evaluation of spinal reflex recovery and histocytological and molecular outcomes. METHODOLOGY: We will use well established in vitro hMSC cultures and organotypic system, as well as our rat model of penetrating SCI (i.e., T9-T10 midline segmental hemisection) to test our hypotheses. Quantitative behavioral batteries, electrophysiology of spinal reflex and sensorimotor tests, and histopathologic assays will be also deployed. Finally, we will perform semi-quantitative Western Blot and quantitative rt-PCR assays for studies that measure expression changes of molecules that play pivotal roles in inflammation, neural plasticity and regeneration. FINDINGS: We have solid pilot and preliminary data to support our hypotheses. Findings obtained from these interlocked and yet independent aims will substantially increase our understanding on in vivo issues of viability and therapeutic interaction of hMSCs for devising polymer and hMSCs based multimechanistic strategies to treat SCI and establish novel therapeutic windows of post-SCI rehabilitation. CLINICAL RELATIONSHIPS: To date, there is still no effective treatment for SCI. Studies proposed in this project are specifically aimed at developing hMSCs into therapeutic regimens to treat paralysis and sensory disorders such as neuropathic pain following SCI. Since PLGA and hMSCs are already in clinical applications for other conditions, our study may introduce a highly effective approach for delivering hMSCs as multimodal anti-degenerative and pro-restorative agents for SCI, traumatic brain injury, and neurodegenerative diseases. IMPACT/SIGNIFICANCE: Effective recovery from traumatic spinal cord injury represents a currently unmet clinical need for about 42,000 US veterans. Our pilot studies demonstrated that hMSCs (a prototype adult stem cell) exert multimechanistic therapeutic effects in neurological systems. These hMSC-derived immunomodulatory and neuroplastic effects could be used to impede degeneration as well as promote restoration and neuroplasticity, which provides a biological foundation for augmenting therapeutic outcomes of SCI rehabilitation.